Friday, November 21, 2008

Flocculation is one of those evolutionary traits of yeast that —Godisgood*— is essential to creating beer.

As any brewer will tell you, the yeast used to make beer tends to bunch up during fermentation. However, despite thousands of years of brewing and decades of genetic research on yeast, no one was able to explain why yeast stuck together.

But now, scientists at Harvard University have at last identified the specific gene that enables yeast to, ahem, flocculate.

That gene allows the normally solitary yeast cells to shield themselves from toxins in their environment by banding together in protective balls. Since one of those toxins is the ethanol that the yeast themselves produce, grouping together allows the yeast to survive in the alcohol-rich environment that results from brewing[emphasis mine].

The gene, called FLO1, produces a Velcro-like protein on the outside of the yeast cells. When a yeast cell bumps into another cell with the same gene, they stick together.

Over time, the yeast cells with FLO1 weed out the freeloaders, pushing them to the outside of the ball. Through this process, the freeloading cells not only don't get the benefit of being in the yeast ball, but they pay a cost by acting as the first line of defense for the yeast flock.

It's almost like game theory for yeast.

And, for Kevin Verstrepen, the lead scientist of the Harvard study, "who got his biology PhD from the Center for Malting and Brewing at the University of Belgium"

this is just one more example of how much the science of beer has to offer the science of biology.

Extrapolating from unicellular biology to group sociology, sometimes it is all about the beer.

* Godisgood: a term once used by brewers to describe the beneficent activity of yeast without understanding its nature. Or maybe they did.